Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$190.46	12.698%	$214.6446	$214.64	$214.65	$214.60
Purchase #2	$249.36	5.307%	$262.5935	$262.59	$262.60	$262.60
Purchase #3	$66.99	8.662%	$72.7927	$72.79	$72.80	$72.80
Purchase #4	$125.56	13.700%	$142.7617	$142.76	$142.75	$142.80
Purchase #5	$86.37	11.428%	$96.2404	$96.24	$96.25	$96.20
Purchase #6	$27.90	13.478%	$31.6604	$31.66	$31.65	$31.70
Purchase #7	$183.95	4.788%	$192.7575	$192.76	$192.75	$192.80
7 purchase totals =	$930.59		$1,013.4508	$1,013.44	$1,013.45	$1,013.50